The present invention generally relates to packaging and more particularly to a method and apparatus for making unitary packages holding a plurality of components with each package containing a load that has a covering of a sheet of material wrapped around it.
Case packing or boxing is a common way of shipping multiple unit products. The multiple unit products are generally stacked in a corrugated box or are wrapped with kraft paper with the ends of the kraft paper being glued or taped. Another way of shipping such products is by putting a sleeve or covering of heat shrinkable film around the products and shrinking it to form a unitized package. The use of heat shrinkable film is described in U.S. Pat. Nos. 3,793,798, 3,626,654, 3,590,509 and 3,514,920. A discussion of this art is set forth in U.S. Pat. No. 3,867,806.
The present invention provides a simple more reliable and cheaper method of unitizing small products into packages.
When the present process and apparatus is compared with other apparatus and processes currently used to pack products in corrugated boxes and the cost of the corrugated boxes themselves, the invention shows an enormous cost savings. The invention has compariable costs with kraft wrap but it gives a much tighter and better unitized package than that possible with kraft wrap. In addition to these factors, the invention has a product visibility which is not present in boxes and kraft wrap. When the invention is compared with most existing shrink film systems the proposed system offers packaging speed, reliability of package seal and energy savings in that less energy is required to package the products.
A basic problem with shrink packaging is that the primary strength and reliability of the package is determined by the consistent quality of the seals. These seals depend on a careful maintenance of the sealing jaw and are never as strong as the film itself. The time that it takes to make the seals is a limiting factor on the possible speeds of most shrink systems.
The present invention does not require any structural seal but maintains the individual cartons or materials which are packaged in a tightly positioned area. In the present invention the system allows for continuous motion in the wrapping process with no critical seals being necessary in the process.
The use of wrapping machinery in the art is known and one such apparatus is shown by U.S. Pat. No. 3,003,297 in which tape is placed by a rotating ring on a box carried by a conveyor line. A complex cutting and holding mechanism is used to place the tape on each box and cut it off with the process being repeated for each box. Another application in packaging is shown by U.S. Pat. No. 3,514,920 in which heat shrink film is wrapped around a pallet supporting a plurality of cartons. Furthermore, it is also known in the art to spirally wrap articles. Such spiral wrapping is shown by U.S. Pat. Nos. 3,788,199, 3,549,077, 3,191,289 and 2,716,315.
The present invention uses stretchable plastic film in its preferred embodiment since the mechanical stretching of the film utilizes its strength better than a heat shrink wrap. The elasticity in the film holds the products in more tension then either the shrink wrap or the kraft wrap particularly with products which settle or relax when packaged.
Various apparatus and processes have been developed by the present inventors to utilize stretch material in package wrapping. Such apparatus and processes are disclosed in U.S. Pat. No. 3,867,806 and U.S. patent application Ser. Nos. 454,477 and 478,523, which have been filed by the present named inventors of this invention. These applications are incorporated herein in their entirety in this application by reference.
Additional benefits occur in the present invention over the prior art in that no changeover is required in handling random size units of a variety of materials as the apparatus is constructed to handle such random size units. Furthermore, the apparatus provides a continuous wrapping operation so that loads can be wrapped at any desired speed. A significant economic factor is also present in the present invention since the power requirements are significantly less than those of shrink systems since there is no heat tunnel required and greater speeds of operation are possible because of the elimination of the conventional heat seal which is used in shrink type wrapping. Because of the simplicity of the construction there is a greater stability of the wrapping apparatus with less maintenance being required to maintain the apparatus and a corresponding reduction in breakdown time.